Date of Award:
8-2024
Document Type:
Thesis
Degree Name:
Master of Science (MS)
Department:
Wildland Resources
Committee Chair(s)
Karen H. Beard
Committee
Karen H. Beard
Committee
Trisha Atwood
Committee
Bonnie Waring
Committee
Andrew Kulmatiski
Abstract
Plants are responsible for a large amount of the movement of carbon (C) and nitrogen (N) through terrestrial systems. One way that plants affect the movement of C and N is through plant litter inputs to soils. Plant litter highly influences processes such as soil microbial respiration and decomposition. Herbivores, such as geese in the Yukon Delta National Wildlife Refuge, affect these processes by changing litter quality and quantity. These changes cause differences in soil respiration, microbial communities, and nutrient turnover. However, because geese influence litter quality, quantity, and habitat characteristics simultaneously, it is not yet clear which of these factors most affects biogeochemical cycling within heavily grazed areas.
To study how these vegetation-herbivore interactions affect the movement of C and N, we performed a litter bag decomposition experiment. Our experiment investigated the potential effects of herbivores on litter decomposition, a vital process for soil organic carbon formation and nutrient turnover. Litter bags contained high and low qualities of litter, and were placed in ‘grazing lawn’ and Carex meadow habitats. ‘Grazing lawn’ is composed of Carex that geese graze, creating short-statured vegetation. Carex meadow is ungrazed habitat that has taller vegetation. Temperature, UV radiation, and rainfall characteristics were monitored between the two habitat types to account for potential habitat differences. We measured carbon and nitrogen content in litter bags.
We also performed a microcosm incubation experiment with soils and litter collected from the Yukon Delta National Wildlife Refuge. We manipulated levels of litter quality and litter quantity to fully examine the effect of litter associated with herbivores. We measured weekly CO2 levels from the microcosms. At the end of the experiment, we sequenced microbial communities and measured soil microbial biomass carbon, dissolved carbon, inorganic nitrogen, and enzyme activity. These factors are associated with differences in C and N, allowing us to see how litter quality and quantity levels affected the movement of C and N.
Our field experiment showed strong associations between litter quality and litter decomposition rates. However, grazed habitats experienced lower decomposition rates than ungrazed Carex meadow habitats. In our lab experiment, quality and quantity affected CO2 levels. Herbivore feces increased CO2 levels. Herbivore feces and low-quality senesced litter cultivated unique microbial communities, showing a strong effect of litter inputs on microbial communities in these soils. Herbivore effects on litter quality and quantity produce vegetation and soil interactions that increase CO2 emissions from soils and increase litter decomposition rates.
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This work is licensed under a Creative Commons Attribution 4.0 License.
Recommended Citation
Saunders, Taylor, "Herbivore Effects on Litter Quality and Quantity and Influences on Carbon Cycling" (2024). All Graduate Theses and Dissertations, Fall 2023 to Present. 299.
https://digitalcommons.usu.edu/etd2023/299
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